1,720,954 research outputs found
Normal modes, surface-wave and time-harmonic body-wave computational modeling and inverse modeling on unstructured, deformable meshes
No full textA novel computational framework is established for modeling normal modes, surface waves and time-harmonic body waves with a combination of several highly parallel algorithms. To deal with complex geological features such as topography and interior discontinuities, both forward modeling and inverse modeling are performed on unstructured, deformable tetrahedral meshes. To study the inverse boundary value problem for time-harmonic elastic waves, for the recovery of P- and S-wave speeds from vibroseis data or the Neumann-to-Dirichlet map, a procedure for full waveform inversion with iterative regularization is designed. The multi-level iterative regularization is implemented by projecting gradients, after scaling, onto subspaces to avoid over-parametrization yielding conditional Lipschitz stability. The procedure is illustrated in computational experiments recovering the rough shapes and wave speeds of geological bodies from simple starting models, near and far from the boundary, that is the free surface. To study the seismic spectra, a Rayleigh-Ritz with mixed continuous Galerkin finite-element method based approach is developed to compute the normal modes of a planet in the presence of an essential spectrum. The relevant generalized eigenvalue problem is solved by a Lanczos approach combined with polynomial filtering and separation of the essential spectrum. Self-gravitation is treated as an N-body problem and the relevant gravitational potential is evaluated directly and efficiently utilizing the fast multipole method. In contrast with the standard shift-and-invert and the full-mode coupling algorithms, the polynomial filtering technique is ideally suited for solving large-scale three-dimensional interior eigenvalue problems since it significantly enhances the memory and computational efficiency without loss of accuracy. The parallel efficiency and scalability of the proposed approach are demonstrated on several world-class supercomputers. To include the effects of the rotation and solve the resulting quadratic eigenvalue problem, the extended Lanczos vectors computed from a non-rotating planet are utilized as a subspace to reduce the dimension of the original problem significantly. The reduced system can further be solved via a standard eigensolver. Several computational experiments are performed to study the effects of the normal modes due to three-dimensional fine variations, rotation, and Coriolis effects
Positive-energy D-bar method for acoustic tomography: A computational study
No full textA new computational method for reconstructing a potential from the Dirichlet-to-Neumann (DN) map at positive energy is developed. The method is based on D-bar techniques and it works in absence of exceptional points - in particular, if the potential is small enough compared to the energy. Numerical tests reveal exceptional points for perturbed, radial potentials. Reconstructions for several potentials are computed using simulated DN maps with and without added noise. The new reconstruction method is shown to work well for energy values between 10-5 and 5, smaller values giving better results
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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